1. Field of the Invention
The present invention relates to a method of and a device for inputting information, particularly coordinates information of a predetermined stroke.
2. Description of the Related Art
Hitherto, transmission of coordinates information from a coordinates input device to a host device is conducted at a predetermined sampling rate, e.g., 100 points per second. Consequently, there are some cases where the information is inadequate in terms of quantity or quality from the view point of processing of such information.
For instance, pieces of information regarding a multiplicity of points as indicated in FIG. 1 by points 1102 to 1109 are transmitted even for a locus of writing that is a simple straight line. More specifically, coordinates information and associated information are transmitted for every 10 msec.
Therefore, it has been a common technique that a host device which processes these types of information generates, for example through a characteristic point extracting device incorporated therein, thinned coordinate information composed solely of characteristic points, for the purpose of processing such information.
Inputting of such a large quantity of information also places a burden on the information receiving section of the host device.
In order to overcome this problem, coordinate input devices have been proposed of the type in which a detected series of coordinate information is examined in terms of the angular displacement between two consecutive coordinate values or the number of coordinate points which have been thinned out consecutively. When a threshold value of the angular displacement or the number of coordinate points has exceeded a predetermined threshold, the coordinate values of the point at which the threshold is exceeded are included as characteristic point coordinate values in the coordinates information series to be transmitted to the host device.
FIGS. 3 to 6 illustrate the manner in which information is output from this type of coordinate input device. For instance, when the locus of writing is substantially straight as shown in FIG. 3, coordinates data of only the points 1302 and 1303, with the intervening point thinned out, are transmitted as characteristic point data. FIG. 4 illustrates this pattern of information output. The information output interval is 60 msec as will be seen from indications of outputs 1409 and 1410.
When the writing locus is curvilinear as shown in FIG. 5, the characteristic points are extracted at a slightly smaller pitch of thinning out than that in FIG. 3. FIG. 6 shows this pattern of information output. Coordinate data are output as indicated by 1605, 1606, 1607 and 1608. The information output interval is 20 m second in this case.
The characteristic point extracting operation as described above, however, encounters with the following problem. Namely, the optimum value of the threshold for extracting the characteristic points varies depending on factors such as the size of the object entering the coordinate input device, the character, pattern or the like, curvatures of curves which constitute such object, velocity of writing, and so forth. Consequently, the host device cannot always receive a coordinate information series which has been thinned out to present only the characteristic points which are optimum for processing by the host device.
When a pattern or the like is input by free-hand writing, the velocity of the writing instrument, e.g., a pen, necessarily occurs at certain points. If such points could be extracted as characteristic points, valuable and useful information for on-line hand-writing recognition or pen-input gesture command recognition would be obtained. With the known technique described above, however, it is impossible to extract such characteristic points, so that such valuable and useful information cannot be obtained.